What is an Adrenal Incidentaloma?

An adrenal incidentaloma (sometimes termed "incidentally found" adrenal mass, or adrenal nodule) is an adrenal growth that is discovered when a radiological scan (X-ray, CT scan, or MRI) is performed for indications other than for adrenal disease. Most commonly adrenal incedentalomas are found on CT scans (CAT scans) of the abdomen for some other reason. By definition, an adrenal incidentaloma excludes adrenal tumors found when the patient is undergoing x-rays and scans as part of a workup of a known cancer that they have elsewhere (for instance, lung, breast, kidney, melanoma).

Are Adrenal Incidentalomas Common?

Adrenal incidentalomas are quite common, and become more common as we age. In autopsy studies of people who died of natural causes, about 6 % of all people have an adrenal mass or adrenal tumor that they were completely unaware of. Therefore small adrenal tumors are common, occuring in about 4-5 percent of us in our lifetime, so you can imagine that lots of people having a CT scan will have an adrenal tumor found that they didn't know about.

Are Adrenal Incidentalomas Cancer?

The vast majority of adrenal incidentalomas are benign and not cancer. Additionally, most adrenal tumors found incidentally do not over-produce any adrenal hormones. Many adrenal incidentalomas can be safely watched without surgery -- typically the patient will get CT scans every 6-12 months or so just to make sure the tumor isn't growing. Remember, adrenal tumors that grow quickly are almost always adrenal cancers.

The rate of adrenal incidentalomas increases with the patient's age. Incidentally found adrenal masses are found in less than 1% in patients younger than 30 yr of age who get an abdominal CT scan, and up to 7% in patients over age 60 who get an abdominal CT scan.

It should be noted, however, that most studies of risk of adrenal tumors found incidentally are flawed in one way or another. Yes, medicine is not a perfect science. For instance, some research studies that have looked at this may be affected by small sample size; inclusion of a patient population who were referred to tertiary centers (introducing bias into the study), inclusion of patients with a history of cancer or suspicion of malignancy (this will increase the rate of identifying adrenal metastasis), and exclusion of patients with small tumors.

Other Cancers Commonly Spread to the Adrenal Glands

In patients who have cancer in another organ, as many as three-fourths of adrenal incidentalomas are found to be metastatic cancer spread to the adrenal gland from the original cancer. The cancers that most commonly spread (metastasize) to the adrenal glands are cancers of the: lung, breast, kidney, and melanoma. In contrast, the lack of a primary cancer site in a patient with an adrenal incidentaloma would make the diagnosis of a metastatic cancer spread to the adrenal gland very unlikely. This is important to know. If you do not have a known cancer somewhere else in your body, then it is very unlikely that the adrenal incidentaloma represents cancer spread (metastasis) from another area of the body.

What Tests Do You Do for Adrenal Incidentalomas?

When clinicians face an adrenal incidentaloma, there are mainly three questions that need to be answered:
  1. Is the mass truly arising from the adrenal? This is usually easy to tell based on the CT or MRI scan. However, there are some rare retroperitoneal lesions that may be adjacent but not arising from the adrenal gland, per se.
  2. Is the adrenal incidentaloma a cancer (malignant), and if so, is it a primary adrenal cancer (the cancer started in the adrenal gland) or is it a metastatic cancer that came from another organ?
  3. Is the incidentaloma functional (overproducing hormones)? Patients with an adrenal incidentaloma should undergo a thorough clinical evaluation including measuring the blood levels of all the adrenal hormones. The history and physical exam should be aimed at excluding a functional tumor or an underlying malignant disease.

Bottom Line: Here are the Percentages of What the Adrenal Incidentaloma Really Is:

1) Adrenal cortical tumors
-- Nonfunctional adenoma 85%
-- Subclinical Cushing's syndrome 6.5%
-- Conn's syndrome 1%
-- Adrenocortical carcinoma 2%
2) Adrenal medullary tumors
-- Pheochromocytoma 3%
3) Metastasis from another distant cancer 1%
4) Others causes <5%